The field of the invention is in the electrical instrumentation art and more particularly in the art of sampling oscilloscopes.
Sampling oscilloscopes are well known. When utilized to measure repeating high frequency electrical waveforms, such devices conventionally employ an electrically strobed probe which samples small sequential portions of successive waveforms. Thus, the cumulative result of this sampling technique provides a composite waveform readout representative of the subject waveforms.
However, certain drawbacks are involved. The electrical strobe of electrical signals often induces spurious results. The dynamic range of conventional probe sampling gates an usually quite limited, i.e., .+-. 1 volt. Though probes may be highly sensitive, the parasitic impedance of the oscilloscope input greatly limits the effective response. Thus, conventional sampling oscilloscopes generally are limited in bandwidth, are subject to spurious results from the strobe, and are limited as to dynamic range when high frequency waveforms are involved. Though the probe may be capable of relatively high speed sampling, the errors generated in providing the resulting signal to the oscilloscope, and particularly parasitic impedance errors, limit the dynamic sensitivity.
Optical switching devices per se are known. However, many of the optical switching devices, such as photodiodes are limited in performance. Further, even with adequate bandwidth and speed, the signals from conventional photosensors are again subject to the errors resulting from parasitic reactances.
In addition, while the electrical strobe is known, the use of such a strobe for measuring the time variation of optical waveforms without the necessity of an intermediate optical to electrical transducer, such as a photodiode, has not heretofore occurred.
A unique device capable of both optical strobing of electrical waveforms and electrical strobing of optical waveforms, as disclosed herein, therefore offers many advantages.
For additional background information helpful in understanding this invention reference is made to the following publications.
Lawton, R. A. and Andrews, J. R., "Pulsed-Laser Application to Sampling Oscilloscope," Electronics Letters, Vol. 11, No. 7, April 1975.
Lawton, R. A. and Scavannec, A. S., "A Photoconductive Detector of Fast Transition Waveforms", Electronics Letters, Vol. 11, pp 74- 75, February 1975.
Andrews, J. R. and Baldwin E. E., "Baseband Impulse Generator Useful to 5 GHz,"1975 IEEE Electromagnetic Compatibility Symposium Record, October 1975, pages 6BId1-6BId4.
Andrews, J. R., "Inexpensive Laser Diode Pulse Generator for Optical Waveguide Studies", Rev. Sci. Instrum., Vol. 45, No. 1, January 1974.
R. Carlson et al, "Sampling Oscillography", Application Note 36, Hewlett-Packard Co.